594 W. M. DAVIS PENEPLAINS AND THE GEOGRAPHICAL CYCLE 



always been to treat the forms of the land in a rational and revolutionary 

 manner. 



Essential Features of the geographical Cycle 



The last point deserves fuller statement. The essence and object of 

 the scheme do not lie in its name, "cycle of erosion/*' to which indeed 

 objection has been made because its processes are not circular in the sense 

 of returning at the end to their beginning — an objection that has less 

 weight today than when it was first offered, because it is now generally 

 recognized that not only must plains and plateaus be in the end worn 

 down to surfaces about as smooth as those with which they began their 

 cycle of change, but also that most of the existing mountain ranges of 

 the world began their present cycle of erosional change in peneplains 

 very much like those down to which they will be again eventually worn 

 if no disturbance happens. Nor do the essence and object of the scheme 

 lie in the adoption of such words as young, mature, and old — two of 

 them, young and old, having been introduced by Chamberlin — as names 

 for the successive stages of an ordinary cycle of erosion; any other names 

 that the geogTaphical world prefers will serve; but it is a satisfaction, 

 quand meme, to know that a physiographer so philosophical as Gilbert 

 held that the analogy on which this terminology is based is good because 

 it indicates a "close resemblance in some striking particulars, coupled 

 with differences in other respects;" and it is truly gratifying to read his 

 opinion : 



"In my judgment, there are few groups of terms which serve better than 

 does this group the purpose of concisely expressing an idea. Its strength 

 inheres, first, in the aptness and completeness of the analogy, and, second, in 

 the perfect familiarity of the group of facts to which the unfamiliar facts 

 are likened. . . . The aptness and the familiarity make the terms perma- 

 nently mnemonic, so that the use of any one of them brings to mind not only 

 the sequence, but relative position in the sequence." 6 



The essence and object of the scheme of the cycle does not lie in its 

 terminology, but in its capacity to set forth the reasonableness of land 

 forms and to replace the arbitrary, empirical methods of description 

 formerly in universal use, by a rational, explanatory method in accord 

 with the evolutionary philosophy of the modern era. All the older 

 descriptions of land forms treated each form by and for itself. The 

 idea that certain groups of forms may be arranged in a genetic sequence 

 based upon structure, process and stage, and the further idea that the 



6 Style in scientific composition. Science, vol. xxi, 1905, pp. 28-29. 



